INFLUENCE OF A CROP ON EVAPORATION 121 



1870 (Jour. Roy. Agri. Soc. 1871, 121). The samples of soil 

 were taken on June 27 and 28. About three-quarters of an 

 inch of rain had fallen in the ten days preceding the taking 

 of the samples. 



TABLE XXI 



WATER PER CENT. OF SOIL AFTER BARLEY AND AFTER 

 FALLOW AT ROTHAMSTED 



Lawes and Gilbert calculate that the barley crop had 

 evaporated 909 tons of water per acre from fifty-four inches 

 of soil, an amount almost exactly equal to nine inches of rain. 



A comparison of the amount of evaporation from a bare 

 soil, and from one covered with turf, is afforded by the 

 results obtained in the different drain-gauges summarized in 

 Table XXII. We have already referred to the amounts of 

 evaporation from a water surface, from the surface of bare 

 loam with flints, and from fine gravel. The results obtained 

 by Greaves with a turfed sandy loam three feet deep, and 

 by Evans with a turfed soil also three feet deep, show a 

 greater evaporation in the whole year (18-1-20-0 inches) 

 than that from the bare loam at Rothamsted (15-9-16-7 

 inches). This difference, however, by no means represents 

 the full evaporating power of the grass turf. The average 

 rainfall in the turf experiments was indeed much less than 



